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## E STIMATING E ARTHWORK

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### ESTIMATING EARTHWORK

Prof Awad S. Hanna

Estimating Earthwork

Earthwork includes:

- 1. Excavation
- 2. Grading: Moving earth to change elevation
- 3. Temporary shoring
- 4. Back fill or fill: Adding earth to raise grade
- 5. Compaction: Increasing density
- 6. Disposal

Prof Awad S. Hanna

Productivity Factors

A. Job conditions

- Material type
- Water level and moisture content
- Job size
- Length of haul
- Haul road condition (accessibility and load restrictions)

Prof Awad S. Hanna

Productivity Factors (cont.)

B. Management conditions

- Equipment conditions and maintenance practices
- Skills of work force and management
- Planning, supervision and coordination of work.

Prof Awad S. Hanna

Job Efficiency Factors for Earthmoving Operations

Prof Awad S. Hanna

1.0 CUBIC YARD IN NATURAL CONDITION (IN-PLACE YARD)

1.25 CUBIC YARD AFTER DIGGING (LOOSE YARDS)

0.90 CUBIC YARD AFTER COMPACTED (COMPACTED YARDS)

1.25

1.0

0.90

In place

Loose

Compacted

Prof Awad S. Hanna

Volume

Bank: VB

- Bank cubic yards (BCY)
- Density B Lb /BCY

Loose: Vl

- Loose cubic yards (LCY)
- Density L Lb/LCY

Compacted: Vc

- Compacted cubic yards (CCY)
- Density C LB/CCY

Prof Awad S. Hanna

Swell:

A soil increase in volume when it is excavated.

Swell (%) = ( - 1) x 100

Load factor =

Bank Volume = Loose volume x Load factor

Bank density

Loose density

Loose density

Bank density

Prof Awad S. Hanna

Shrinkage:

A soil decreases in volume when it is compacted

Shrinkage (%) = (1 - ) x 100

Shrinkage factor = 1 - Shrinkage

Compacted volume

= Bank volume x Shrinkage factor

Bank density

Compacted density

Prof Awad S. Hanna

Approximate Material Characteristics

- Exact values will vary with grain size, moisture content, compaction, etc. Test to determine exact values for specific soils.

Prof Awad S. Hanna

Typical Soil Volume Conversion Factors

Prof Awad S. Hanna

Approximate Angle of Repose

For Sloping Sides of Excavation

Recommended Slope for Average Soils

1:1 (45 Deg.)

Compacted Angular Gravels

1/2:1 (63 Deg.)

Compacted Sharp Sand

1 1/2 :1 (33 Deg.)

Well Rounded Loose Sand

2:1 (26 Deg.)

Original

Ground Line

Solid Rock, Slate or Cemented Sand and Gravel

(90 Deg.)

Prof Awad S. Hanna

CALCULATING EARTHWORK QUANTITIES

1. End Area Method

a. Take cross-sections at regular intervals, typically, 100’ intervals.

b. Calculate the cross-section end areas

c. The volume of earthwork between sections is obtained by taking the average of the end areas at each station in square feet multiplied by the distance between sections in feet and dividing by 27 to obtain the volume in cubic yards.

Prof Awad S. Hanna

Project Site Showing 100 Stations

C’

E’

B’

D’

F’

A’

78

86

80

88

84

82

82

80

300'

84

Fill

Cut

86

88

C

E

F

B

D

A

100'

100'

100'

100'

100'

500'

Prof Awad S. Hanna

Sec. A’- A

78.5

78

76

82

Sec. B’- B

80.3

80

78

84

Sec. C’- C

82.3

82

Project Cross Sections

80

86

Sec. D’- D

84.2

84

88

Sec. E’- E

86.2

86

90

Sec. F’- F

88.2

88

Prof Awad S. Hanna

Cross-Section @ A- A

80

107 x 1.0

Area = = 53.5

79.5

2

79

78.5

78

77

193 x 1.8

76.7

Area = = 173.7

2

76

Section A’- A

Prof Awad S. Hanna

Cross-Section @ B- B

82

81.8

90 x 1.5

Area = = 67.5

2

81

80.3

80

79

210 x 1.8

76.7

Area = = 189.0

2

78

Section B’- B

Prof Awad S. Hanna

Table 1. Cumulative Earthwork Quantities

Prof Awad S. Hanna

2. Contour Line/ Grid Method

- Used for parking lots and site “leveling”
- Grid size from 10’x10’ to 50’x50’
- the greater the terrain variance the smaller the grid

Prof Awad S. Hanna

2. CONTOUR LINE/GRID CELL METHOD(cont.)

Step l

Determine by visual study of the site drawing if the net total will be an import (more fill required than cut) an export (less fill required than cut) or a blend (cut and fill about equal)

Step 2

Determine the pattern of calculation points or grid size.

Step 3

Determine elevations at each calculation location, the corners of each grid.

Step 4

Calculate the cubic yards of cut or fill required in each grid cell.

Step 5

Add the individual Grid Cell quantities together to arrive at the total cut, total fill volume and the import or volume export yardage required for the job.

Prof Awad S. Hanna

C

E

B

D

F

G

300’

88’

89’

90’

91’

92’

93’

94’

87.6

88.5

89.3

90.3

91.5

95.0

A

C

E

B

D

F

87.6

88.6

89.4

90.4

91.6

93.2

94.3

G

J

L

H

K

M

87.4

88.2

89.5

90.6

91.6

92.7

93.5

N

P

R

O

Q

S

87.2

87.7

89.0

90.4

91.3

92.0

93.1

Notes:

1. Bring the entire site to elevation 90.

2. All grids are 50’x 50’ = 2500 sq. ft.

3. Present contours

No Scale

Prof Awad S. Hanna

- Purpose

Grade the entire site to grade 90’

- Quick and Dirty

Assume one grid

Existing 90.50

Proposed 90.00

Cut 0.50

Total Cost = = 833CY

Need

Fill

Need

Cut

150'

300'

90'

91'

90.5'

150 x 300 x 0.50

27

Prof Awad S. Hanna

If we choose the grid size to be 50’x50’

88.6

Average elevation

=

= 88.08

change = 90-88.08

= 1.92

cut =

= 177.77 CY

and so on.

87.6

87.6+88.5+87.6+88.6

4

87.6

87.6

Prof Awad S. Hanna

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